3 DSL LInes

[timothha22]

My boss wanted us to take advantage of cheap internet connectivity. So now we have 3 DSL lines and 1 T1. I plan to use the 3 DSL lines for internet surfing from office employees and the T1 for business web site and application use. My question is I now have a 2851 cisco router. It has a HWIC 4SEW 4 port switch card in the back of it. It also has the CSU DSU card for the T1. I was told I could use the 4 port card to configure the DSL's using VLAN's to allow the users to surf the internet. I need to know how to load balance these and if I could do fail over to the T1 if the DSL line where to fail. Would I use something like OSPF? I am newbie to the CISCO router world so if you have any questions please let me know. Something like round robin would be great for the DSL's. I am not sure if that is possible?

 

[lanbrown]

In order for OSPF to work, your ISP's would have to participate. I would forget about the use of a routing protocol. I would like to add I would never try to do what you’ve been asked to.

Does the web server reside on the same network as the users? If so, you would have to use a route-map statement to make sure the web server went out the T1. You would also need to have three default routes for the Internet, all with the same cost. The downside to this is if a DSL line went down, the router would never know. It will use if the VLAN is up or not, so if a DSL line goes down, that VLAN will still remain up. With three DSL lines, that would give you a 33.3% drop packet rate. If you could put DSL WICs in the router, which would do what you are after. Lastly, there would be no way to fail over to the T1. A routing protocol is the only way and you won't find a DSL provider willing to do it. I would go to your boss and say his idea is not feasible with the equipment on hand.

If you could deal with two DSL lines, you could do the route-map for the web server to use the T1. For the two DSL lines, you could use a Linksys router, like the RV042 or RV082, which allows the use of two Internet connections. You can set one as primary and the other a backup, or do load sharing. Then you would just need one default route for the users. If you really need three DSL lines, you could do the above, but with two Linksys routers with two default routes. This would still leave you with a problem if the DSL line on the Linksys with just eats goes down, but with a 50% drop rate instead of 33.3%. In order to get around this, four DSL lines could be used, two on each. If one DSL lines goes down in that scenario, packets would not get dropped. To go one-step further, I would look at two DSL providers, each will provide two DSL lines. Linksys router "A" would have one DSL line from each provider; Linksys router "B" would be setup the same. If one provider has an issue, you wouldn't get the 50% drop rate as you would if one provider was on one router.

May I ask how many users and how much bandwidth you really need? Is Internet that really important? Is cable offered in your area? Some cable companies are offering 6 or 8 Mbps. You could getaway with the above setup, but one cable and one DSL. That would provide a higher level of availability then just DSL and guarantee different providers and paths.

 

[timothha22]

Thanks for your help Lanbrown. Sorry for the delay I went home from work Friday and took the weekend off.

Could I put DSL wics in the router and do what my boss wants? Load balancing with failover?

We have about 250 users. We currently use 1 T1 in which the bandwidth is maxed out on. Cable is not offered in our area we checked on it to do exactly what you are suggesting. We also can only get DSL with one provider.

 

[lanbrown]

Maybe. First I would see what type of DSL service is being offered and if Cisco has a WIC that can use it. If they do, look at the cost, which might be a deciding factor. Next, what fail-over could you possibly have? All three lines will go to one DSLAM, if that fails, all the lines will be out. The only fail-over you will really have is if one port on the DSLAM has an issue. Guess how often that happens?